PCT Patent applications PCT/EP02/04651, PCT/EP02/04646, PCT/EP02/04650 and PCT/EP02/04648 describe a system for measuring heat liberated or absorbed by a chemical or physical reaction. This information can be used for measuring and controlling reaction efficiency in steady state processes and reaction progress in unsteady state processes. The control is affected by measuring the temperature change in the heat transfer fluid to determine the quantity of heat liberated or absorbed by the reaction and adjusting the area of temperature control surface available to the reaction accordingly.
The earlier patent applications describe a system containing a series of heat transfer coils where individual heat transfer coils are designed such that the heat transfer area of the heat transfer pipe is matched (approximately given that U varies with flow, temperature and liquid properties and it varies with application) with the flow carrying capacity of the liquid such that:U.A.LMTD=m.Cp.(tsi-tso)(kW)where U=overall heat transfer coefficient (kW.m−2.K−1)                A=heat transfer area (m2)        m=mass flow rate of heat transfer fluid (kg/s)        LMTD=log mean thermal difference between service and process fluids (° C.)        Cp=specific heat of heat transfer fluid (kJ.kg−1K-−1)        (tsi-tso)=temperature (° C.) change in the heat transfer fluid between inlet and outlet        
The system described in PCT Patent applications PCT/EP02/04651, PCT/EP02/04646, PCT/EP02/04650 and PCT/EP02/04648 is a variable area heat transfer system. Multiple coils are used in combination to match the desired operating conditions. The ability to transition between these coils in a smooth, bounce-less manner is of great importance to the stability of the system. Poor accuracy of the heat measurements can result from a crudely implemented system. The system described in the PCT Patent applications PCT/EP02/04651, PCT/EP02/04646, PCT/EP02/04650 and PCT/EP02/04648 utilizes multiple control and switching valves to bring individual coils into or out of operation. This is however a complicated system which can involve jumps in the system as one switches a new coil into action or as one switches a coil out of action. The use of a multi-port flow control valve, which whilst achieving a high degree of control also offers the additional benefits of a compact design, reduces the amount of control signals required and enables smoother transitions.